A dispenser supplying a predetermined amount of liquid that is in liquid form, such as water, oil, or resin is used in various fields such as in a semiconductor process or in the medical field.
Particularly in a semiconductor process, a dispenser is frequently used in an underfill process to fill a package of a semiconductor device with a resin. In a process of manufacturing a light emitting diode (LED) device, a dispenser is used in a process of coating a LED chip of the LED device with a phosphorescent liquid in which a phosphorescent material and a resin are mixed.
The dispenser as described above includes, as a core element, a pump that receives a liquid and dispenses a fixed amount of the liquid to an exact position.
Various pumps structures such as a screw pump or a linear pump are available. Recently, a piezoelectric pump that uses a piezoelectric element as an actuator has been developed and used in a semiconductor process or the like to perform a dispensing operation at a high speed.
KR 2005-0079557 (published on Aug. 10, 2005) discloses a piezoelectric pump structure comprising a plurality of piezoelectric actuators, on which a piezoelectric element is attached, and which are sequentially operated in connection with one another at different displacement differences to pump a fluid.
A piezoelectric actuator used in a piezoelectric pump is usually formed of a ceramic material. Most piezoelectric actuators including such ceramic piezoelectric actuators generate heat when operating according to an applied voltage. When a temperature of the piezoelectric actuator increases due to heat generated in the piezoelectric actuator, dynamic characteristics of the piezoelectric actuator are changed, and the lifetime of the piezoelectric actuator is also reduced.
Thus, a piezoelectric pump or a piezoelectric dispenser having a structure capable of preventing an increase in a temperature of a piezoelectric actuator is required.